Photosynthesis in Plants

Blackman (1905) discovered that photosynthesis consists of two distinct phases: the light reactions and the dark reactions. The dark reactions (light-independent reactions) don't directly require light but use the products of light reactions. Calvin later elucidated the specific pathway (Calvin cycle) of the dark reaction.

During tomato ripening, chloroplasts (which contain green chlorophyll) break down and disappear. Simultaneously, chromoplasts (plastids containing red pigments like lycopene) develop and become visible. This transformation from chloroplasts to chromoplasts causes the color change from green to red.

When respiration exceeds photosynthesis, the plant consumes more carbohydrates than it produces, depleting its energy reserves. This negative energy balance leads to starvation and gradual death, as the plant cannot sustain its metabolic functions without sufficient energy production.

The green color of Green Hydra comes from symbiotic Zoochlorella algae (Chlorella) living within the endodermal cells of the hydra. This is an example of mutualism where the algae provide food through photosynthesis and receive protection. The color is not due to pigments in epidermis, endodermis, or mesoglea.

This enzyme is needed in dark reaction.

This is the correct answer as all the statements given above are correct. Chromoplasts are coloured plastids. Leucoplasts are colourless plastids. Leucoplasts are involved in the formation and storage of starch and oil drops.

Photosynthetic bacteria like purple sulfur bacteria and green sulfur bacteria do not use water as an electron donor. Instead, they use hydrogen sulfide (H2S) or other inorganic compounds, producing sulfur or sulfate as byproducts rather than oxygen. Blue-green algae (cyanobacteria), green algae, and autotrophic plants all use water and release oxygen during photosynthesis.

Bacteria contain photosynthetic pigments in chromatophores, which are infoldings of the cell membrane containing pigments like bacteriochlorophyll. Chloroplasts, chromoplasts, and leucoplasts are types of plastids found in plant and algal cells, not bacteria. Bacteria lack membrane-bound organelles like plastids, so their photosynthetic apparatus is membrane-associated in chromatophores.

Photorespiration occurs when RuBisCO binds O2 instead of CO2, which happens more under high O2 and low CO2 conditions. High temperature also promotes photorespiration by reducing CO2 solubility. Humidity affects transpiration but not directly photorespiration.

This is the correct option. Carbon dioxide, water, chlorophyll and sunlight are the necessary components for photosythesis. The green plants have chlorophyll in their leaves. The leaves use carbon dioxide and water to make food in the presence of sunlight. 

This is the correct option, as the statement is false. Oxygen from air is taken in through the stomata present on the surface of the leaves, is a false statement. It is carbon dioxide, not oxygen that is taken in through the stomata present on the surface of the leaves.

Ribulose is the pentose sugar that forms the backbone of ribulose-1,5-bisphosphate (RuBP), the molecule that accepts carbon dioxide in the first step of the Calvin cycle. The enzyme RuBisCO catalyzes the carboxylation of RuBP, making it absolutely essential for carbon fixation in all photosynthetic organisms.

Taeniophyllum (a leafless orchid) contains chlorophyll in its aerial roots for photosynthesis, an unusual adaptation. Most roots lack chlorophyll entirely. Pothos, piper, and laranthus (likely typo for loranthus) are typical plants with chlorophyll only in stems and leaves.

Brown algae (Phaeophyta) like Laminaria and Fucus are rich sources of iodine, concentrated in their cell walls. Red and blue-green algae lack significant iodine content. 'Epidermis' in option D is anatomical nonsense in this context.